Prefabricated panel modules are desirable for use in buildings and other kinds of construction because of their versatility and low cost. Modules are mass-produced in various standard sizes for engagement to adjacent modules of similar configuration. Typically, each module is fabricated of two parallel, spaced, rectangular metal face panels joined by laterally extending end structures along opposite edges. The prefabricated modules are typically connected in edge-to-edge relationship by seam welding.
The modules are especially suitable for constructing security walls and ceilings of cells in correctional facilities, where many of the cells are of repetitive design and construction. The modules are fabricated of steel and therefore inherently resistant to vandalism, fire, and destruction by inmates.
The usefulness of these modules, particularly in prison construction, is severely limited because the joints conduct heat across the modules, and also from one module to another. In addition, sound is easily transmitted through the joints, across the modules and from one module to another, reducing privacy and, in the case of prison cells, compromising security.
In one proposed alternative construction, the opposed face panels of a module are insulated from each other by means of a seal such as glass fiber rope compressed between mating elements of the face panels. This helps to reduce sound transmission and heat transfer between panels of a module. However, adjacent modules are secured together by welding in metal-to-metal contact. Thus no adequate provision is made for thermal or sound insulation between the adjacent modules. Furthermore, welding adjacent modules together on-site is labor intensive and consequently expensive.
In another proposed alternative construction, modules having ship-lap joints are used. Insulation strips are interposed between the joint elements of adjoining modules, and between the opposed face panels of each of the modules, to provide thermal and sound insulation between adjacent modules as well as to reduce heat and noise conduction across the wall. In the ship-lap joint, it has been generally thought necessary to install the insulating strips on-site. Until the present invention, there has been no satisfactory, structurally simple, way of providing factory-installed insulation strips in a ship-lap joint
Another problem in ship-lap joints is that it is necessary in many cases to use a screw or similar fastener to secure adjoining modules together. Tamper-resistant screw heads, i.e. heads capable of being turned by a screwdriver in the tightening direction only, can be used, but are not entirely satisfactory in a prison environment.